The present invention relates generally to semiconductor fabrication, and more specifically to apparatus for storing and transporting semiconductor wafers.
FIG. 1 shows a conventional assembly 10 for transporting semiconductor wafers 40. A container 20 has a box bottom 22 and a box cover 24. Inside the container 20 is a wafer carrier or cassette 30 that holds a plurality of semiconductor wafers 40. The wafer carrier 30 is a tray having a plurality of slots formed between adjacent pairs of ribs 34. Although only one pair of ribs 34 is visible in FIG. 1, one of ordinary skill understands that a plurality of ribs are arranged from front to back in planes parallel to the ribs 34 shown in FIG. 1. A respective slot is formed between each successive set of ribs 34. Each slot is capable of storing a respective wafer 40. Although only one wafer 40 is shown in FIG. 1, one of ordinary skill understands that a plurality of wafers are arranged from front to back in planes parallel to wafer 40. The box 20 with the wafer carrier 30 and wafers 40 inside may be transported between different processing stations, typically on wheeled carts.
The exemplary wafer carrier 30 also has right and left rearwardly projecting tabs 36 on its bottom, extending in a direction perpendicular to the plane of FIG. 1. A pair of stiffening ribs 38 are integrally formed at the front and rear ends of the wafer carrier 30. A structural cross member 32 is provided in the front of the wafer carrier 30, and a similar cross member is present in the back. The wafer carrier 30 is typically made from a carbon impregnated polypropylene material or similar material. Exemplary wafer carrier systems such as that shown in FIG. 1 are manufactured by Entegres, Inc., Chaska, Minn. (formerly Fluoroware, Inc.).
Because they contain a large number of wafers 40 in known positions, the wafer carriers 30 are useful in automated semiconductor processing. The wafers 40 can be automatically removed from the wafer carrier 30 for processing in an automated wafer processing system (not shown). For example, an ion implant system includes various wafer handling mechanisms for transferring semiconductor wafers into and out of the ion implanter. Some ion implant systems include a wafer clamp for transferring semiconductor wafers from the wafer carrier in which they are stored, onto an ion implanter disk. The wafer clamp grasps the wafer while it is disposed in the carrier, removes it from the carrier, and places it on the ion implanter disk.
Experience with wafer handling systems has shown that, after transport, upon removal from the wafer carrier, wafers often have an unacceptable number of contaminant particles on their surfaces. These contaminant particles interfere with the processing of the wafers.
An improved method and system for handling semiconductor wafers is desired.
One aspect of the invention is an insert for a container. The container is shaped to contain a wafer carrier during transport. The wafer carrier is shaped to hold a plurality of semiconductor wafers. The insert has a size and shape so as to snugly fit in a predetermined position in the container. The insert has at least one mounting feature to snugly hold the wafer carrier.
Another aspect of the invention is an assembly for storing semiconductor wafers, including: a container, a wafer carrier and a plate to which the wafer carrier is attached. The wafer carrier fits in the container. The wafer carrier has a plurality of slots, each slot capable of receiving a semiconductor wafer. The plate has a size and shape so as to snugly fit in a predetermined position in the container and substantially prevent movement of the wafer carrier relative to the container.
Another aspect of the invention is a method for handling at least one semiconductor wafer. an insert is snugly fitted in the bottom of a container. A wafer carrier is mounted on the insert. At least one semiconductor wafer is inserted in the wafer carrier. The container is transported with the insert, wafer carrier and at least one wafer contained therein.
The above and other features of the present invention will be better understood from the following detailed description of the exemplary embodiment of the invention which is provided in connection with the accompanying drawings.